/// <summary>
/// Visits the TryBlock.
///
/// Returns a new State object representing the exceptional control flow transfer out of the try block.
/// </summary>
protected State HandleTryBlock(TryInstruction inst)
{
State oldStateOnException = currentStateOnException;
State newStateOnException;
if (stateOnException.TryGetValue(inst, out newStateOnException))
{
newStateOnException.JoinWith(state);
}
else
{
newStateOnException = state.Clone();
stateOnException.Add(inst, newStateOnException);
}
currentStateOnException = newStateOnException;
inst.TryBlock.AcceptVisitor(this);
// swap back to the old object instance
currentStateOnException = oldStateOnException;
// No matter what kind of try-instruction this is, it's possible
// that an async exception is thrown immediately in the handler block,
// so propagate the state:
oldStateOnException.JoinWith(newStateOnException);
return(newStateOnException);
}
public virtual void Visit(TryInstruction instruction)
{
}
private string TryReduceTry(BasicBlock root, TryBasicBlock trybb)
{
var group = new Set<BasicBlock> { trybb };
var leavetrybb = trybb.Body as LeaveTryBasicBlock;
if (leavetrybb == null || leavetrybb.HandlerPopCount != 1)
return null;
group.Add(leavetrybb);
var handlers = new Seq<TryInstructionHandler>();
foreach (var tbbHandler in trybb.Handlers)
{
var catchh = tbbHandler as TBBCatchHandler;
if (catchh != null)
{
if (!(catchh.Body is NonReturningBasicBlock))
{
// If body is not already free of control flow, check if it can be made to fall
// through to after try
var leavecatchbb = catchh.Body as LeaveCatchBasicBlock;
if (leavecatchbb == null || leavecatchbb.HandlerPopCount != 1 ||
!leavecatchbb.Target.Equals(leavetrybb.Target))
return null;
if (!group.Add(leavecatchbb))
// Should never happen
return null;
}
// else: catch ends with a return, throw, rethrow, break or continue
// Catch body WILL NOT end with leave
handlers.Add(new CatchTryInstructionHandler(catchh.Type, catchh.Body.Block));
}
else
{
var faulth = tbbHandler as TBBFaultHandler;
if (faulth != null)
{
// Body must be an end fault
var endfaultbb = faulth.Body as EndFaultBasicBlock;
if (endfaultbb == null)
return null;
if (!group.Add(endfaultbb))
// Should never happen
return null;
// Fault handler body WILL NOT end with endfinally/endfault
handlers.Add(new FaultTryInstructionHandler(endfaultbb.Block));
}
else
{
var finallyh = tbbHandler as TBBFinallyHandler;
if (finallyh != null)
{
// Body must be an end finally
var endfinallybb = finallyh.Body as EndFinallyBasicBlock;
if (endfinallybb == null)
return null;
if (!group.Add(endfinallybb))
// Should never happen
return null;
// Finally handler body WILL NOT end with endfinally/endfault
handlers.Add(new FinallyTryInstructionHandler(endfinallybb.Block));
}
else
throw new InvalidOperationException("unrecognized handler");
}
}
}
// Try body WILL NOT end with leave
var tryi = new TryInstruction(NextInstructionId--, leavetrybb.Block, handlers)
{ BeforeState = trybb.Block.BeforeState, AfterState = leavetrybb.Block.AfterState };
var newbb = new JumpBasicBlock(nextBlockId++, new Instructions(tryi), leavetrybb.Target);
root.Coalesce(trybb, group, newbb);
return String.Format("structural try/catch/finally/fault from B{0}", trybb.Id);
}
public virtual void Visit(TryInstruction instruction)
{
Default(instruction);
}